"Non HP Cartridge detected" ...but it IS an HP toner

[DCO57]

We have 700+ network printers at my site (big site). We always use official HP toner cartiridges.In the past we would see a "Non HP Cartridge detected" error about 3 or 4 times a year.... now we're seeing it 3 or 4 times a week. This is mainly happening with our HP 4600 color Laserjets.
Could it be that these toner cartirdges are getting older and are being recycled (and refilled) over and over? Could it be "killer chips" (embedded in the cartidge) that I've been hearing about that time out after 100,000 or so prints? Or maybe its just the sensors on the printers that are going bad.
Has anyone else seen an increase in this error?
Thanks
DCO / IBM

[MichaelTech]

Whoa! 100,000? Try 8-9000. The toner sensor may be dirty, or going bad.
The toner life is within 2.5 yrs., but dont count on it. "Off the shelf" may be a year or more old.
Check dates! Do not trust your supplier.

[cs_steve]

Cleaning the contacts is one option that may help... clean both the contacts on the cartridge and within the printer.

Fortunately, this is not a fatal error so your users can continue printing even with the Cartridge warning displayed.